Initiator device, responder device, and system

ABSTRACT

An initiator device ( 102 ) is provided with a generation circuit ( 810 ) for supporting Single User (SU)-Multiple Input Multiple Output (MIMO) operation and generating a first signal ( 602, 652 ) including a value that indicates which of a reciprocal MIMO phase and a non-reciprocal MIMO phase is to be applied to SU-MIMO BF training, and a transmission circuit ( 820 ) for transmitting the first signal ( 602, 652 ) to a responder device ( 104 ). The responder device ( 104 ) is provided with a reception circuit ( 820 ) for receiving the first signal ( 602, 652 ) from the initiator device ( 102 ), and a processing circuit ( 830 ) for determining on the basis of the value which of the reciprocal MIMO phase and the non-reciprocal MIMO phase is to be applied to SU-MIMO BF training.

TECHNICAL FIELD

The present disclosure relates to an initiator device, a responderdevice, and a system.

BACKGROUND ART

The unlicensed 60 GHz millimeter wave (mmW) network has been attractinga growing interest. The WirelessHD technology is the first 60 GHz mmWindustry standard that enables multi-gigabit wireless streaming ofhigh-definition audio, video, and data among home electronic appliances,personal computers, and mobile products. Another multi-gigabit wirelesscommunication technology that operates via a 60 GHz mmW frequency bandis the WiGig technology standardized as the IEEE 802.11ad standard byInstitute of Electrical and Electronic Engineers (IEEE). With a broadchannel bandwidth of 2.16 GHz, the WiGig technology realizes a physicallayer (PHY) data transfer speed of up to 6.7 gigabits per second (Gbps).The IEEE 802.11 Working Group is developing an 802.11ay wirelessinterface as a next-generation WiGig technology capable of supporting aPHY data transfer speed higher than 100 Gbps. The single user(SU)-multiple input multiple output (MIMO) technique, in which pluralspatial streams are simultaneously transmitted through plural spatialpaths, is one of major techniques for 802.11ay.

802.11ay widely uses beamforming (BF) to achieve directionaltransmission, unlike other IEEE 802.11 technologies that operate via a2.4 GHz or 5 GHz frequency band. In the 60 GHz mmW frequency band, asignal wavelength is smaller than a normal size of an object in apropagation environment, and thus beam-like propagation with discretespatial signal paths spreads. A signal quality, for example, asignal-to-noise ratio (SNR), can be significantly improved in a casewhere both a transmit (TX) antenna beam and a receive (RX) antenna beammatch a strong spatial signal path.

CITATION LIST Non-Patent Literature NPL 1

IEEE 802.11-17/1041r0, CR on SU-MIMO & MU-MIMO BF training and feedback,July 2017

NPL 2

IEEE 802.11-16/1620r2, 3.1.4 MIMO Channel Access, January 2017

NPL 3

IEEE 802.11-17/1184r2, MU-MIMO BF Selection, August 2017

NPL 4

IEEE Std 802.11TM-2016, Section 10.38 beamforming, December 2016

SUMMARY OF INVENTION Technical Problem

Studies are in progress to execute efficient BF training for an SU-MIMOoperation.

Solution to Problem

An initiator device according to one aspect of the present disclosure isa device that supports a single user (SU)-multiple input multiple output(MIMO) operation, including: a generation circuit that generates a firstsignal including a value indicating which of a reciprocal MIMO phase anda non-reciprocal MIMO phase is applied to SU-MIMO beamforming (BF)training; and a transmission circuit that transmits the first signal toa responder device.

A responder device according to one aspect of the present disclosure isa device that supports a single user (SU)-multiple input multiple output(MIMO) operation, including: a reception circuit that receives from aninitiator device a first signal including a value indicating which of areciprocal MIMO phase and a non-reciprocal MIMO phase is applied toSU-MIMO beamforming (BF) training; and a processing circuit thatdetermines, on the basis of the value, which of the reciprocal MIMOphase and the non-reciprocal MIMO phase is applied to the SU-MIMO BFtraining.

A system according to one aspect of the present disclosure includes: aninitiator device and a responder device that support a single user(SU)-multiple input multiple output (MIMO) operation, in which theinitiator device includes a generation circuit that generates a firstsignal including a value indicating which of a reciprocal MIMO phase anda non-reciprocal MIMO phase is applied to SU-MIMO beamforming (BF)training, and a transmission circuit that transmits the first signal tothe responder device, and in which the responder device includes areception circuit that receives the first signal from the initiatordevice, and a processing circuit that determines, on the basis of thevalue, which of the reciprocal MIMO phase and the non-reciprocal MIMOphase is applied to the SU-MIMO BF training.

Note that, these comprehensive or specific aspects may be realized by asystem, an apparatus, a method, an integrated circuit, a computerprogram, or a recording medium, and/or may be realized by an optionalcombination of a system, an apparatus, a method, an integrated circuit,a computer program, and a recording medium.

Advantageous Effects of Invention

According to one aspect of the present disclosure, it is possible torealize efficient BF training for an SU-MIMO operation.

Additional benefits and advantages of one aspect of the presentdisclosure will become apparent from the specification and drawings. Thebenefits and/or advantages may be individually obtained by someembodiments and features described in the specification and drawings,which need not all be provided in order to obtain one or more of suchfeatures.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating an SU-MIMO operation in a wirelesssystem;

FIG. 2 is a diagram illustrating a non-reciprocal MIMO phase of SU-MIMOBF training;

FIG. 3A is a schematic configuration diagram of a station (STA)according to the present disclosure;

FIG. 3B is a detailed configuration diagram of the STA according to thepresent disclosure;

FIG. 4 is a diagram illustrating an example of a format of an actionfield of a MIMO BF setup frame according to Embodiment 1;

FIG. 5 is a diagram illustrating an example of a format of a MIMO setupcontrol element according to Embodiment 1;

FIG. 6 is a diagram illustrating an example of a format of an enhanceddirectional multi-gigabit (EDMG) beam refinement protocol (BRP) packetaccording to Embodiment 1;

FIG. 7 is a diagram illustrating a reciprocal MIMO phase of SU-MIMO BFtraining according to Embodiment 1;

FIG. 8A is a diagram illustrating an example of a digital BF procedureaccording to Embodiment 1;

FIG. 8B is a diagram illustrating another example of the digital BFprocedure according to Embodiment 1;

FIG. 9 is a diagram illustrating access to an SU-MIMO channel afterSU-MIMO BF training according to Embodiment 1;

FIG. 10 is a diagram illustrating a downlink MIMO phase of MU-MIMO BFtraining according to Embodiment 1;

FIG. 11 is a diagram illustrating an uplink MIMO phase of MU-MIMO BFtraining according to Embodiment 1;

FIG. 12 is a flowchart for setting information fields of a MIMO setupcontrol element according to Embodiment 1;

FIG. 13 is a flowchart for interpreting the information fields of theMIMO setup control element according to Embodiment 1;

FIG. 14 is a diagram illustrating a reciprocal MIMO phase of SU-MIMO BFtraining according to Modification Example 1;

FIG. 15 is a diagram illustrating a reciprocal MIMO phase of SU-MIMO BFtraining according to Modification Example 2;

FIG. 16 is a diagram illustrating a reciprocal MIMO phase of SU-MIMO BFtraining according to Modification Example 3;

FIG. 17 is a diagram illustrating an example of a digital BF procedureaccording to Modification Example 3;

FIG. 18 is a diagram illustrating an example of a format of a MIMO setupcontrol element according to Embodiment 2;

FIG. 19 is a flowchart for setting information fields of a MIMO setupcontrol element according to Embodiment 2; and

FIG. 20 is a flowchart for interpreting the information fields of theMIMO setup control element according to Embodiment 2.

DESCRIPTION OF EMBODIMENTS

Hereinafter, embodiments of the present disclosure will be described indetail with reference to the drawings.

The technique described in the present disclosure can be applied to manywireless communication systems. For the purpose of exemplification, thefollowing description in the present disclosure will be given about anIEEE 802.11-based wireless local area network (WLAN) system and therelated terminologies thereof. This should not be understood aslimitation of the present disclosure about alternative wirelesscommunication systems.

FIG. 1 illustrates an SU-MIMO operation in wireless system 100 (asystem). Wireless system 100 includes initiator 102 and responder 104.Initiator 102 and responder 104 each include plural array antennas. Theplural array antennas support a single user (SU)-multiple input multipleoutput (MIMO) operation using plural spatial streams configured to formone antenna beam/sector for each array antenna. A sector is one ofconfigurations for directional control and is referred to by using asector ID defined in the 802.11ay standard. Hereinafter, a sector may beread as an antenna weighting vector (AWV). An AWV may be used in thecase of performing signaling (feedback) in which the correspondence witha sector ID is not fixed, for example, like an AWV used in the third TRNsubfield of a BRP frame, which will be described below.

<SU-MIMO BF Training>

Before executing an SU-MIMO operation, analog beamforming training(SU-MIMO BF training) is applied to the plural array antennas ofinitiator 102 and responder 104 to determine recommended TX/RX sectorcombinations (for example, best TX/RX sector combinations) fortransmitting plural spatial streams. Here, in a case where TX/RXrepresents transmission by initiator 102 and reception by responder 104,TX/RX sector combinations mean a TX sector combination of initiator 102and a (best) RX sector combination of responder 104 for an initiatorlink in which initiator 102 performs transmission and responder 104performs reception. In a case where TX/RX represents transmission byresponder 104 and reception by initiator 102, TX/RX sector combinationsmean a TX sector combination of responder 104 and a (best) RX sectorcombination of initiator 102 for a responder link in which responder 104performs transmission and initiator 102 performs reception.

TX antennas and RX antennas are capable of forming, in each arrayantenna, one TX sector and one RX sector, respectively. Thus,recommended TX/RX sector combinations for MIMO transmission each belongto a specific TX/RX antenna pair. Furthermore, in a case where thenumber of TX antennas is equal to the number of RX antennas, all TX/RXantenna pairs to which the recommended TX/RX sector combinations belongdo not overlap in the meaning that any TX antenna or any RX antennabelongs only to a single TX/RX antenna pair. This is because, in a casewhere there is an overlap among the TX/RX antenna pairs, a certain TXantenna or RX antenna is not involved in an SU-MIMO operation. In thiscase, the maximum number of spatial streams that is equal to the minimumnumber of TX antennas and RX antennas cannot be supported.

For example, in the TX/RX antenna pairs (TX1-RX2, TX2-RX1) in Table 1given below, TX antennas TX1 and TX2 belong to one TX/RX antenna pairTX1-RX2 and one TX/RX antenna pair TX2-RX1, respectively. Also, RXantennas RX1 and RX2 belong to one TX/RX antenna pair TX2-RX1 and oneTX/RX antenna pair TX1-RX2, respectively. In this case, the number oftwo MIMO streams, equal to the maximum number of spatial streams, thatis, the minimum number of TX antennas and RX antennas, is supported.

TABLE 1 <Table 1> TX/RX antenna pairs and the number of MIMO streamssupported TX/RX antenna pairs Number of MIMO streams supported (TX1-RX2,TX2-RX1) 2 (TX1-RX1, TX1-RX2) 1 (TX1-RX1, TX2-RX1) 1

In contrast to this, in the TX/RX antenna pairs (TX1-RX1, TX1-RX2) inTable 1, TX antenna TX1 belongs to both two TX/RX antenna pairs TX1-RX1and TX1-RX2. Thus, the two TX/RX antenna pairs TX1-RX1 and TX1-RX2overlap, and the other TX antenna TX2 is not involved in an SU-MIMOoperation. In this case, the number of one MIMO stream, smaller than twoequal to the maximum number of spatial streams, that is, the minimumnumber of TX antennas and RX antennas, is supported.

As a result of the SU-MIMO BF training, TX antenna settings andcorresponding RX antenna settings can be determined for simultaneoustransmission of plural spatial streams from initiator 102 to responder104 or from responder 104 to initiator 102. In addition, the SU-MIMO BFtraining makes it possible to perform a transmission BF operation and areception BF operation between initiator 102 and responder 104. A singlespatial stream is transmitted between initiator 102 and responder 104via plural antennas that use the determined TX antenna settings. Also, asingle spatial stream is received via plural antennas that use thedetermined corresponding RX antenna settings.

The SU-MIMO BF training is formed of two consecutive phases, a singleinput single output (SISO) phase and a MIMO phase. The SISO phase aimsat collecting, by initiator 102, feedback from responder 104 oninitiator transmit sector sweep executed last during or before the SISOphase, and collecting, by responder 104, feedback from initiator 102 onthe last responder transmit sector sweep. The MIMO phase aims attraining TX/RX sectors and TX/RX antennas to determine recommended TX/RXsector combinations and TX/RX antenna combinations for an SU-MIMOoperation.

<SU-MIMO BF Training: Non-Reciprocal MIMO Phase>

FIG. 2 illustrates a non-reciprocal MIMO phase of SU-MIMO BF training. AMIMO phase (non-reciprocal MIMO phase) of 802.11ay SU-MIMO BF trainingis formed of four subphases, an SU-MIMO BF setup subphase, an initiatorSU-MIMO BF training (I-SMBT) subphase, a responder SMBT (R-SMBT)subphase, and an SU-MIMO BF feedback subphase.

In the SU-MIMO BF setup subphase, initiator 102 first transmits MIMO BFsetup frame 202 to responder 104. Hereinafter, a frame is an example ofa signal. MIMO BF setup frame 202 includes setting information to beused by responder 104 in the R-SMBT subphase.

MIMO BF setup frame 202 indicates the number N_(tsc(I)) of TX sectorcombinations requested for an initiator link and the number of TRNsubfields requested for RX AWV training in the subsequent R-SMBTsubphase. In addition, on the basis of the SNRs of TX sectors collectedfrom responder 104 in the SISO phase, initiator 102 is capable ofselecting a subset of candidate TX sectors for each antenna to reducethe time required for training of I-SMBT.

Note that, in a case where initiator 102 has antenna patternreciprocity, the subset of candidate TX sectors for each antennaselected by initiator 102 for the I-SMBT subphase can be used to reducethe number of TRN subfields to be used for RX AWV training in thesubsequent R-SMBT subphase.

Subsequently, after receiving MIMO BF setup frame 202 from initiator102, responder 104 transmits MIMO BF setup frame 204 to initiator 102.MIMO BF setup frame 204 includes setting information to be used byinitiator 102 in the I-SMBT subphase.

MIMO BF setup frame 204 indicates the number N_(tsc(R)) of TX sectorcombinations requested for a responder link and the number of TRNsubfields requested for RX AWV training in the subsequent I-SMBTsubphase. In addition, on the basis of the SNRs of TX sectors collectedfrom initiator 102 in the SISO phase, responder 104 is capable ofselecting a subset of candidate TX sectors for each antenna to reducethe time required for training of R-SMBT.

Note that, in a case where responder 104 has antenna patternreciprocity, the subset of candidate TX sectors for each antennaselected by responder 104 for the R-SMBT subphase can be used to reducethe number of TRN subfields required for RX AWV training in thesubsequent I-SMBT subphase.

After receiving MIMO BF setup frame 204 from responder 104, initiator102 starts the initiator SMBT (I-SMBT) subphase. In the I-SMBT subphase,initiator 102 performs initiator SU-MIMO BF training. Initiator 102transmits EDMG BRP-RX/TX packets 210 to responder 104 via plural TXantennas.

EDMG BRP-RX/TX packets 210 each include plural TRN subfields transmittedfor responder 104 to perform training of receive sectors and AWVs.Responder 104 receives EDMG BRP-RX/TX packets 210 while switching thereceive sectors and receive AWVs, thereby being capable of performingtraining of the receive sectors and AWVs. Initiator 102 transmits EDMGBRP-RX/TX packets 210 while switching transmit sectors, thereby beingcapable of performing training of the transmit sectors. That is, EDMGBRP-RX/TX packets 210 are packets for evaluating (training) combinationsof TX sectors of the initiator and RX sectors and AWVs of the responder.The number of TRN subfields of each EDMG BRP-RX/TX packet 210 isconfigured in accordance with TRN configuration information in MIMO BFsetup frame 204 received from responder 104.

Responder 104 receives EDMG BRP-RX/TX packets 210 via plural RX antennasand trains different TX/RX sector combinations for the initiator link.

Subsequently, after receiving last EDMG BRP-RX/TX packet 212 frominitiator 102, responder 104 starts the responder SMBT (R-SMBT)subphase. In the R-SMBT subphase, responder 104 transmits EDMG BRP-RX/TXpackets 220 to initiator 102 via plural TX antennas.

EDMG BRP-RX/TX packets 220 are packets similar to EDMG BRP-RX/TX packets210 described above except that initiator 102 and responder 104 arereplaced with responder 104 and initiator 102, respectively. The numberof TRN subfields of each EDMG BRP-RX/TX packet 220 is configured inaccordance with TRN configuration information in MIMO BF setup frame 202received from initiator 102 in the SU-MIMO BF setup subphase.

Initiator 102 receives EDMG BRP-RX/TX packets 220 via plural RX antennasand trains different TX/RX sector combinations for the responder link.

Subsequently, after receiving last EDMG BRP-RX/TX packet 222 fromresponder 104, initiator 102 starts the SU-MIMO BF feedback subphase. Inthe SU-MIMO BF feedback subphase, initiator 102 transmits MIMO BFfeedback frame 232 to responder 104.

MIMO BF feedback frame 232 indicates N_(tsc(R)) recommended (forexample, best) TX sector combinations for the responder link that aredetermined on the basis of channel measurement data acquired from theR-SMBT subphase. Here, the responder link is a link from responder 104to initiator 102. MIMO BF feedback frame 232 includes the SNRscorresponding to the N_(tsc(R)) recommended TX sector combinations. MIMOBF feedback frame 232 is capable of including channel measurementresults corresponding to the N_(tsc(R)) recommended TX sectorcombinations.

Subsequently, after receiving MIMO BF feedback frame 232 from initiator102, responder 104 transmits MIMO BF feedback frame 234 to initiator102.

MIMO BF feedback frame 234 indicates N_(tsc(I)) recommended (forexample, best) TX sector combinations for the initiator link that aredetermined on the basis of channel measurement data acquired from theI-SMBT subphase. Here, the initiator link is a link from initiator 102to responder 104. MIMO BF feedback frame 234 includes the SNRscorresponding to the N_(tsc(I)) recommended TX sector combinations. MIMOBF feedback frame 234 includes channel measurement results correspondingto the N_(tsc(I)) recommended TX sector combinations.

According to the present disclosure, in the non-reciprocal MIMO phase ofSU-MIMO BF training illustrated in FIG. 2, N_(tsc(I)) recommended TXsector combinations (or equivalent N_(tsc(I)) recommended TX-RX AWVconfigurations) for the initiator link and N_(tsc(R)) recommended TXsector combinations (or equivalent N_(tsc(R)) recommended TX-RX AWVconfigurations) for the responder link are determined by using a methodin which TX or RX AWVs are not derived from the same antenna.

Initiator 102 and responder 104 need to train all combinations of TX/RXsectors, and the execution of SU-MIMO BF training requires a long time.The present disclosure has been conceived to reduce the time requiredfor SU-MIMO BF training.

Embodiment 1 <Configuration of STA>

FIG. 3A is a schematic configuration diagram of STA 800 according to thepresent disclosure. FIG. 3B is a detailed configuration diagram of STA800 according to the present disclosure. STA 800 is an example ofinitiator 102 or responder 104 according to the present disclosure. STA800 includes transmission signal generation circuit 810 (a generationcircuit), transceiver 820 (a transmission circuit and/or a receptioncircuit), received signal processing circuit 830 (a processing circuit),and control circuit 840. For example, transmission signal generationcircuit 810, received signal processing circuit 830, and control circuit840 may be packaged as a MAC processing circuit.

Transmission signal generation circuit 810 generates a transmissionsignal. Transmission signal generation circuit 810 includes messagegeneration circuit 812. Message generation circuit 812 generates asignal under control by control circuit 840. The signal is a data signalor a control signal and is, for example, a packet or a frame. The datasignal and control signal that are generated are, for example, a MIMO BFsetup frame, a BRP frame, and a MIMO BF feedback frame.

Transceiver 820 transmits a generated signal. In addition, transceiver820 receives a radio signal. Transceiver 820 includes PHY processingcircuit 822 and plural antennas 824. PHY processing circuit 822 performsPHY processing on a signal generated by message generation circuit 812.The signal that has been subjected to PHY processing is converted from abaseband signal into a radio frequency signal and is transmitted viaplural antennas 824.

Received signal processing circuit 830 processes a received signal.Received signal processing circuit 830 includes message processingcircuit 832. Message processing circuit 832 processes (analyzes) areceived signal under control by control circuit 840 and provides thesignal to control circuit 840. The received signal is a data signal or acontrol signal and is, for example, a packet or a frame.

Control circuit 840 is a PHY and media access control (MAC) protocolcontroller and controls an entire PHY and MAC protocol operation.Control circuit 840 includes BF control circuit 842 that controls analogBF and hybrid BF operations according to the present disclosure (forexample, SU-MIMO BF training and the subsequent digital BF procedure).BF control circuit 842 determines TX sectors and RX sectors (recommendedTX sectors and RX sectors) to be used for MIMO transmission by STA 800.

<Format>

FIG. 4 illustrates an example of a format of an action field of a MIMOBF setup frame according to Embodiment 1. As illustrated in FIG. 4, theMIMO BF setup frame includes, as a part of the action field, a MIMOsetup control element as the fourth piece of information.

FIG. 5 illustrates an example of a format of MIMO setup control element400 according to Embodiment 1. MIMO setup control element 400 is used toconvey configuration information about SU-MIMO BF training and feedbacksubphases or MU-MIMO BF training and feedback subphases.

MIMO setup control element 400 includes an SU/MU field, anon-reciprocal/reciprocal SU-MIMO phase field, a DL/UL MU-MIMO phasefield, and a link type field.

The SU/MU field indicates that, for example, when the value is 1,SU-MIMO BF training is intended. The SU/MU field indicates that, forexample, when the value is 0, multi-user MIMO (MU-MIMO) BF training isintended.

The non-reciprocal/reciprocal SU-MIMO phase field indicates that, forexample, when the value is 1, the non-reciprocal MIMO phase illustratedin FIG. 2 is applied to SU-MIMO BF training. Thenon-reciprocal/reciprocal SU-MIMO phase field indicates that, forexample, when the value is 0, the reciprocal MIMO phase illustrated inFIG. 7 is applied to SU-MIMO BF training. When the value of the SU/MUfield is 0, the non-reciprocal/reciprocal SU-MIMO phase field is areserved field.

The DL/UL MU-MIMO phase field indicates whether a downlink MIMO phase(see FIG. 10) or an uplink MIMO phase (see FIG. 11) is applied toMU-MIMO BF training. This field is reserved for SU-MIMO BF training.

The link type field indicates whether the configuration information isinformation about the initiator link or information about the responderlink.

In Embodiment 1, in a case where the non-reciprocal MIMO phase isapplied to SU-MIMO BF training, a value indicating that thenon-reciprocal MIMO phase is applied is set to MIMO BF setup frame 202illustrated in FIG. 2. For example, the value of the SU/MU field and thevalue of the non-reciprocal/reciprocal SU-MIMO phase field of the MIMOsetup control element in MIMO BF setup frame 202 illustrated in FIG. 2are set to 1 in the case of indicating that the nonreciprocal MIMO phaseis applied to SU-MIMO BF training.

Furthermore, the value of the link type field is set to 1 in a casewhere the configuration information included in MIMO BF setup frame 202is information about the initiator link. Furthermore, the SU/MU fieldand the non-reciprocal/reciprocal SU-MIMO phase field of MIMO BF setupframe 204 are set in the same manner as the corresponding fields of MIMOBF setup frame 202.

In other words, in a case where the non-reciprocal MIMO phase is appliedto SU-MIMO BF training, both the value of the SU/MU field and the valueof the non-reciprocal/reciprocal SU-MIMO phase field of the MIMO setupcontrol element in MIMO BF setup frame 204 are set to 1.

Furthermore, in a case where the configuration information included inMIMO BF setup frame 204 is information about the responder link, thevalue of the link type field is set to 0.

In Embodiment 1, the value set to the MIMO BF setup frame in a casewhere the reciprocal MIMO phase is applied to SU-MIMO BF training willbe described below with reference to FIG. 7.

FIG. 6 illustrates an example of a format of an EDMG BRP packetaccording to Embodiment 1. A packet is an example of a signal. The EDMGBRP packet includes data field 502 and TRN field 504. Data field 502includes a BRP frame. TRN field 504 includes plural TRN subfields and isconfigured in accordance with the type of the EDMG BRP packet. Forexample, TRN field 504 of an EDMG BRP-TX packet is configured to trainone or plural TX sectors, whereas TRN field 504 of an EDMG BRP-RX/TXpacket is configured to train one or plural TX sectors and some RX AWVsof each TX sector.

<SU-MIMO BF Training: Reciprocal MIMO Phase>

A case is considered in which both initiator 102 and responder 104 haveantenna pattern reciprocity. Here, antenna pattern reciprocity is aproperty in which the characteristics of TX antennas and RX antennasused for MIMO transmission match in each direction and the best TXsector and the best RX sector match. In this case, initiator 102 maystart a reciprocal MIMO phase for SU-MIMO BF training.

FIG. 7 illustrates a reciprocal MIMO phase of SU-MIMO BF trainingaccording to Embodiment 1. The reciprocal MIMO phase illustrated in FIG.7 includes three subphases, an SU-MIMO BF setup subphase, an I-SMBTsubphase, and an SU-MIMO BF feedback subphase. In the reciprocal MIMOphase, it is possible to omit the packets corresponding to EDMGBRP-RX/TX packets 220 of R-SMBT for the responder link and the framecorresponding to MIMO BF feedback 232 for R-SMBT among the frames andpackets illustrated in FIG. 2 transmitted and received in thenon-reciprocal MIMO phase.

In the SU-MIMO BF setup subphase, initiator 102 transmits MIMO BF setupframe 602 to responder 104. In Embodiment 1, the values of the SU/MUfield and the non-reciprocal/reciprocal SU-MIMO phase field of the MIMOsetup control element in MIMO BF setup frame 602 are set to 1 and 0,respectively, to indicate that the reciprocal MIMO phase is applied toSU-MIMO BF training. The value of the link type field is set to 1 in acase where the configuration information included in MIMO BF setup frame602 is information about the initiator link. MIMO BF setup frame 602indicates the number N_(tsc(I)) of TX sector combinations requested forthe initiator link. In addition, on the basis of the SNRs of TX sectorscollected from responder 104 in the SISO phase, initiator 102 is capableof selecting (setting) a subset of candidate TX sectors for each antennawith a decreased number of TRN subfields to reduce the time required fortraining of I-SMBT.

After receiving MIMO BF setup frame 602 from initiator 102, responder104 transmits MIMO BF setup frame 604 to initiator 102.

The values of the SU/MU field and the non-reciprocal/reciprocal SU-MIMOphase field of MIMO BF setup frame 604 are set to the same values as thevalues of the corresponding fields of MIMO BF setup frame 602. In otherwords, the values of the SU/MU field and the non-reciprocal/reciprocalSU-MIMO phase field of MIMO BF setup frame 604 are set to 1 and 0,respectively, to indicate that the reciprocal MIMO phase is applied toSU-MIMO BF training. The value of the link type field is set to 1 in acase where the configuration information included in MIMO BF setup frame604 is information about the initiator link.

Furthermore, MIMO BF setup frame 604 indicates the number of training(TRN) subfields requested for RX AWV training in the subsequent I-SMBTsubphase. On the basis of the SNRs of TX sectors collected frominitiator 102 in the SISO phase, responder 104 is capable of selecting asubset of candidate RX sectors for each antenna with a decreased numberof TRN subfields to reduce the time required for training of I-SMBT.

After receiving MIMO BF setup frame 604 from responder 104, initiator102 starts the I-SMBT subphase. In the I-SMBT subphase, initiator 102transmits EDMG BRP-RX/TX packets 610 (a first BRP packet) to responder104. The number of TRN subfields of each EDMG BRP-RX/TX packet 610 isconfigured in accordance with TRN configuration information in MIMO BFsetup frame 604 received from responder 104 in the SU-MIMO BF setupsubphase.

After receiving last EDMG BRP-RX/TX packet 612 from initiator 102,responder 104 starts the SU-MIMO BF feedback subphase. Responder 104transmits MIMO BF feedback frame 622 (a first MIMO BF feedback frame) toinitiator 102. MIMO BF feedback frame 622 indicates N_(tsc(I))recommended (for example, best) TX sector combinations for the initiatorlink that are determined on the basis of channel measurement dataacquired from the I-SMBT subphase. MIMO BF feedback frame 622 includesthe SNRs corresponding to the N_(tsc(I)) recommended TX sectorcombinations. MIMO BF feedback frame 622 may include channel measurementresults corresponding to the N_(tsc(I)) recommended TX sectorcombinations.

In Embodiment 1, in the reciprocal MIMO phase of SU-MIMO BF trainingillustrated in FIG. 7, N_(tsc(I)) recommended TX sector combinations (orequivalent N_(tsc(I)) recommended TX-RX AWV configurations) for theinitiator link are determined by using a method in which TX or RX AWVsare not derived from the same antenna. The N_(tsc(I)) recommended TX/RXsector combinations (for example, best TX/RX sector combinations)determined for the initiator link are handled as N_(tsc(R)) recommendedRX/TX sector combinations for the responder link. Note thatN_(tsc(I))=N_(tsc(R)).

On the basis of the recommended RX/TX sector combinations for theresponder link, initiator 102 determines a recommended RX sectorcombination to be used by initiator 102 for the responder link. Therecommended RX sector combination to be used by initiator 102 for theresponder link may be the same as the recommended TX sector combinationto be used by initiator 102 for the initiator link.

On the basis of the recommended RX/TX sector combinations for theresponder link, responder 104 determines a recommended TX sectorcombination to be used by responder 104 for the responder link. Therecommended TX sector combination to be used by responder 104 for theresponder link may be the same as the recommended RX sector combinationto be used by responder 104 for the initiator link.

In Embodiment 1, the above-described reciprocal MIMO phase is used inaddition to or instead of the above-described non-reciprocal MIMO phase,as a MIMO phase of SU-MIMO beamforming. Initiator 102 determines whetherthe non-reciprocal MIMO phase or the reciprocal MIMO phase is to be usedin SU-MIMO BF training in responder 104. In a case where initiator 102or responder 104 does not have antenna pattern reciprocity, in otherwords, in a case where the TX antenna pattern related to an AWV is notthe same as the RX antenna pattern of the same AWV, the non-reciprocalMIMO phase is used. In a case where both initiator 102 and responder 104have antenna pattern reciprocity, either the non-reciprocal MIMO phaseor the reciprocal MIMO phase can be used.

<Hybrid BF>

In Embodiment 1, after SU-MIMO BF training including the MIMO phaseillustrated in FIG. 2 or FIG. 7 has been completed, initiator 102 andresponder 104 are capable of executing a digital BF procedure of ahybrid BF operation. The digital BF procedure enables a baseband beamformer to be determined on the basis of the antenna configurationdetermined as a result of the SU-MIMO BF training.

FIG. 8A illustrates an example of a digital BF procedure according toEmbodiment 1. In the example of the digital BF procedure illustrated inFIG. 8A, digital BF is applied to the responder link.

First, responder 104 transmits control trailer (CT) 702 a and grantframe 702 to initiator 102. Here, CT 702 a includes informationindicating the antenna configuration used for the responder link in thedigital BF procedure.

Subsequently, after successfully receiving grant frame 702, initiator102 transmits CT 704 a and grant acknowledgement (grant ack) frame 704to respond to responder 104. Here, CT 704 a includes informationindicating the antenna configuration used for the initiator link in thedigital BF procedure.

Subsequently, responder 104 transmits CT 706 a and ready to send (RTS)frame 706 to initiator 102 to access a channel, and makes a notificationabout the start of the digital BF procedure for the responder link.Here, CT 706 a includes information indicating the antenna configurationused for the responder link in the digital BF procedure.

Subsequently, after successfully receiving RTS frame 706, initiator 102transmits CT 708 a and directional multi-gigabit (DMG) clear to send(CTS) frame 708 to respond to responder 104. Here, CT 708 a includesinformation indicating the antenna configuration used for the initiatorlink in the digital BF procedure. Furthermore, initiator 102 configuresarray antennas for the responder link on the basis of the antennaconfiguration information in grant ack frame 704.

Subsequently, responder 104 transmits EDMG BRP-TX packet 712 (a secondBRP packet), which will be described below with reference to FIG. 6,thereby sounding a channel for the initiator link (transmits a signalfor channel measurement). EDMG BRP-TX packet 712 is transmitted with theantenna configuration for the responder link based on the result of theSU-MIMO BF training illustrated in FIG. 2 or FIG. 7.

Subsequently, initiator 102 transmits MIMO BF feedback frame 714 (asecond MIMO BF feedback frame) including the SNR, MIMO channelmeasurement, or digital precoding matrix information for the responderlink, to respond to responder 104.

As a result of the above-described procedure, initiator 102 obtainsfeedback of the SNR for the responder link by using hybrid BF, anddetermines an appropriate modulation and coding scheme (MC S) on thebasis of the SNR.

FIG. 8B illustrates another example the digital BF procedure accordingto Embodiment 1. In the example of the digital BF procedure illustratedin FIG. 8B, digital BF is applied to the initiator link.

First, initiator 102 transmits CT 702 a and grant frame 702 to responder104. Here, CT 702 a includes information indicating the antennaconfiguration used for the initiator link in the digital BF procedure.

Subsequently, after successfully receiving grant frame 702, responder104 transmits CT 704 a and grant ack frame 704 to respond to initiator102. Here, CT 704 a includes information indicating the antennaconfiguration used for the responder link in the digital BF procedure.

Subsequently, initiator 102 transmits CT 706 a and RTS frame 706 toresponder 104 to access a channel, and makes a notification about thestart of the digital BF procedure for the initiator link. Here, CT 706 aincludes information indicating the antenna configuration used for theinitiator link in the digital BF procedure.

Subsequently, after successfully receiving RTS frame 706, responder 104transmits CT 708 a and DMG CTS frame 708 to respond to initiator 102.Here, CT 708 a includes information indicating the antenna configurationused for the responder link in the digital BF procedure. Furthermore,responder 104 configures array antennas for the responder link on thebasis of the antenna configuration information in grant ack frame 704.

Subsequently, responder 104 transmits EDMG BRP-TX packet 712 (the secondBRP packet), which will be described below with reference to FIG. 6,thereby sounding a channel for the responder link (transmits a signalfor channel measurement). EDMG BRP-TX packet 712 is transmitted with theantenna configuration for the responder link based on the result of theSU-MIMO BF training illustrated in FIG. 2 or FIG. 7.

Subsequently, initiator 102 transmits MIMO BF feedback frame 714 (thesecond MIMO BF feedback frame) including the SNR, MIMO channelmeasurement, or digital precoding matrix information for the responderlink, to respond to responder 104.

In a case where measurement of the initiator link is performed by usingBRP frames 610 in FIG. 7, BRP frame 712 is used to perform measurementof the responder link. Although measurement of the responder link isomitted in the SU-MIMO BF training illustrated in FIG. 7 and measurementof the initiator link is omitted in FIG. 8A or FIG. 8B, the SNRs of boththe initiator link and the responder link can be measured.

As a result of the above-described procedure, responder 104 obtainsfeedback of the SNR for the responder link by using hybrid BF, anddetermines an appropriate modulation and coding scheme (MCS) on thebasis of the SNR.

The non-reciprocal/reciprocal SU-MIMO phase field described above withreference to FIG. 5 may be included in CT 702 a, 704 a, 706 a, or 708 adescribed above with reference to FIG. 8A and FIG. 8B in addition to orinstead of MIMO setup control element 400. In a case where responder 104or initiator 102 designates reciprocal in CT 702 a, initiator 102 orresponder 104 omits transmission of a BRP frame. Thus, the executiontime of the digital BF procedure illustrated in FIG. 8A or FIG. 8B canbe shortened and the power consumption can be reduced.

In the digital BF procedure illustrated in FIG. 8B, responder 104 maytransmit a DMG CTS to Self frame instead of DMG CTS 708. Here, the DMGCTS to Self frame is a frame for notifying another STA that responder104 will perform transmission after the DMG CTS to Self frame by settingresponder 104 as both the source and destination addresses. Theoperation of transmitting a DMG CTS to Self frame as a response to RTSframe 706 is not specified in an existing standard, such as the 11adstandard, but the frame exchange order conforms to the existingstandard.

In a case where the value of the non-reciprocal/reciprocal SU-MIMO phasefield included in CT 706 a of RTS frame 706 indicates reciprocal,transmission of BRP 712 after transmission of DMG CTS 708 may bepermitted, and the execution of DMG CTS to Self may be permitted aftertransmission of RTS 706. Initiator 102 notifies responder 104 by settinga value indicating reciprocal in the non-reciprocal/reciprocal SU-MIMOphase field, thereby being capable of assuming that responder 104transmits frames in an order different from that according to the 11adstandard. Thus, responder 104 is capable of performing DMG CTS to Selfthat is not defined in the 11ad standard in response to RTS frame 706,without increasing the complexity of control. In addition, responder 104is capable of transmitting BRP 712 without increasing the complexity ofcontrol after transmitting DMG CTS 708.

<Access to SU-MIMO Channel>

FIG. 9 illustrates access to an SU-MIMO channel after the SU-MIMO BFtraining according to Embodiment 1 (FIG. 7) or after the SU-MIMO BFtraining illustrated in FIG. 2. Initiator 102 and responder 104 performthe SU-MIMO BF training illustrated in FIG. 2 or FIG. 7 and thenaccesses the SU-MIMO channel by using a recommended TX sectorcombination determined through the training.

First, initiator 102 transmits CT 402 a and grant frame 402 to responder104. Here, CT 402 a includes information indicating that SU-MIMOtransmission is to be used and information indicating a recommended TXsector combination to be used in SU-MIMO data transmission or a digitalBF procedure for the initiator link.

Subsequently, after successfully receiving grant frame 402, responder104 transmits CT 404 a and grant ack frame 404 to respond to initiator102. Here, CT 404 a includes information indicating that MIMO RX can beprepared by a target time, information indicating which of the initiatorand the responder was the transmission source of CT 404 a during theSU-MIMO BF training, and information indicating a recommended

TX sector combination to be used in SU-MIMO data transmission or adigital BF procedure for the responder link. Note that, in the SU-MIMOBF training illustrated in FIG. 2 or FIG. 7 and the SU-MIMO channelaccess illustrated in FIG. 9, the initiator and the responder may changeplaces.

Furthermore, CT 404 a includes an SU-MIMO transmission configurationtype field. Here, the SU-MIMO transmission configuration type field is afield indicating that a recommended TX sector combination can beobtained from the SU-MIMO BF training and feedback for the responderlink or the initiator link. For example, in a case where the value ofthe SU-MIMO transmission configuration type field is 0, the SU-MIMOtransmission configuration type field includes information indicatingthat a recommended TX sector combination can be obtained from theSU-MIMO BF training and feedback for the initiator link.

In a case where recommended TX/RX sector combinations determined for theinitiator link are respectively handled as recommended RX/TX sectorcombinations for the responder link, initiator 102 may operate under theassumption that a recommended TX sector combination can be obtained fromthe SU-MIMO BF training and feedback for the initiator link withoutreferring to the SU-MIMO transmission configuration type field.

For example, in a case where the value of the SU-MIMO transmissionconfiguration type field of CT 404 a is 0, initiator 102 uses, as arecommended RX sector combination for the responder link, a recommendedTX sector combination of initiator 102 indicated by grant frame 402.

Furthermore, responder 104 sets, by using antenna pattern reciprocity, arecommended TX sector combination to be used by responder 104 as arecommended RX sector combination of responder 104 corresponding to therecommended TX sector combination of initiator 102 indicated by grantframe 402.

Subsequently, initiator 102 transmits CT 406 a and RTS frame 406 toinitiator 102 to access a channel. Here, CT 406 a includes, like CT 402a, information indicating that SU-MIMO transmission is to be used andinformation indicating a recommended TX sector combination to be used inSU-MIMO data transmission or a digital BF procedure for the initiatorlink.

Subsequently, after successfully receiving RTS frame 406, responder 104transmits CT 408 a and DMG CTS frame 408 to respond to initiator 102.Here, CT 408 a includes information indicating that MIMO RX is prepared,information indicating that SU-MIMO transmission is to be used in areverse direction, and information indicating a recommended TX sectorcombination to be used in SU-MIMO data transmission or a digital BFprocedure for the responder link. Furthermore, CT 408 a includes, likeCT 404 a, an SU-MIMO transmission configuration type field.

Subsequently, after successfully receiving DMG CTS frame 408, initiator102 transmits data frame 410 to responder 104 by using the recommendedTX sector combination indicated by CT 406 a. In response to reception ofdata frame 410, responder 104 transmits ack frame 412 to respond toinitiator 102.

<MU-MIMO BF Training>

According to Embodiment 1, MU-MIMO BF training enables initiator 102 andone or plural responders 104 in a group to establish an antennaconfiguration that enables initiator 102 to transmit EDMG MU PPDU to theresponders in the group such that mutual interference between streamstransmitted in a physical layer protocol data unit (PPDU) is minimized.MU-MIMO BF training includes a SISO phase and a MIMO phase that areconsecutive.

The SISO phase collects feedback about TX of one or plural appropriateinitiators and RX antennas of a responder, and sectors between theinitiators and each responder in a group. The collected information maybe used to execute the subsequent MIMO phase. The MIMO phase includes adownlink MIMO phase or an uplink MIMO phase. An SU-MIMO operation and anMU-MIMO operation are each an independent operation, and a terminalcompatible with both the operations may perform either of them first.

<MU-MIMO BF Training: Downlink MIMO Phase: Non-Reciprocal MIMO Phase>

FIG. 10 illustrates a downlink MIMO phase of MU-MIMO BF trainingaccording to Embodiment 1. The downlink MIMO phase includes foursubphases, an MU-MIMO BF setup subphase, an MU-MIMO BF trainingsubphase, an MU-MIMO BF feedback subphase, and an MU-MIMO BF selectionsubphase.

In the MU-MIMO BF setup subphase of the downlink MIMO phase, initiator102 first determines the number M of responders 104 in a group forperforming training, on the basis of designation by the EDMG group andthe group user mask illustrated in FIG. 5 in which the correspondencewith a set of MAC addresses is predetermined. Subsequently, initiator102 transmits one or plural MIMO BF setup frames 902 to M responders 104in the group.

According to Embodiment 1, the SU/MU field and the DL/UL MU-MIMO phasefield of the MIMO setup control element in MIMO BF setup frame 902 areset to 0 and 1, respectively, to indicate that the downlink MIMO phaseis applied to MU-MIMO BF training. In addition, on the basis of the SNRsof TX sectors collected from the responders in the SISO phase, initiator102 is capable of selecting a subset of candidate TX sectors for eachantenna to reduce the time required for MU-MIMO BF training.

After transmitting MIMO BF setup frames 902, initiator 102 starts theMU-MIMO BF training subphase. In the MU-MIMO BF training subphase,initiator 102 transmits EDMG BRP-RX/TX packets 910 to responders 104.

After transmitting last EDMG BRP-RX/TX packet 912, initiator 102 startsthe MU-MIMO BF feedback subphase. In the MU-MIMO BF feedback subphase,initiator 102 sequentially transmits MIMO BF polling frames to poll theindividual responders in the group and collect MU-MIMO BF feedback.

Each responder 104 receives MIMO BF polling frame 920. Each responder104 checks an address written on MIMO BF polling frame 920 and, in acase where a corresponding address is written, corresponding responder104 transmits MIMO BF feedback frame 922 to initiator 102. The MIMO BFfeedback frame indicates the SNR that has been obtained via channelmeasurement data acquired from the MU-MIMO BF training subphase and thatcorresponds to N_(tsc) recommended TX sector combinations and N_(tsc)recommended TX sector combinations. The MIMO BF feedback frame caninclude a channel measurement result corresponding to the N_(tsc)recommended TX sector combinations. Here, N_(tsc) means N_(tsc(I)). Inthe downlink MIMO phase illustrated in FIG. 10, MU-MIMO training in thedownlink direction is performed, and there is no responder link. Thus,N_(tsc(I)) is referred to as N_(tsc) for simplicity.

Prior to MU-MIMO BF feedback, initiator 102 polls each responder 104,and starts the MU-MIMO BF selection subphase after receiving a MIMO BFfeedback frame from M-th responder 104, that is, last responder 104 inthe group. In the MU-MIMO BF selection subphase, initiator 102 transmitsone or plural MIMO BF selection frames 930 to individual responders 104in the group. Each MIMO BF selection frame includes information about anMU-MIMO transmission configuration.

<MU-MIMO BF Training: Uplink MIMO Phase: Reciprocal MIMO Phase>

In a case where initiator 102 has antenna pattern reciprocity, initiator102 starts an uplink MIMO phase of MU-MIMO BF training.

FIG. 11 illustrates an uplink MIMO phase of MU-MIMO BF trainingaccording to Embodiment 1. The uplink MIMO phase includes threesubphases, an MU-MIMO BF setup subphase, an MU-MIMO BF trainingsubphase, and an MU-MIMO BF selection subphase.

In the MU-MIMO BF setup subphase of the uplink MIMO phase, initiator 102transmits one or plural MIMO BF setup frames 1002 to individualresponders 104 in the group. According to Embodiment 1, both the SU/MUfield and the DL/UL MU-MIMO phase field of the MIMO setup controlelement in MIMO BF setup frame 1002 are set to 0 to indicate that theuplink MIMO phase is applied to MU-MIMO BF training.

After transmitting MIMO BF setup frames 1002, initiator 102 starts theMU-MIMO BF training subphase. In the MU-MIMO BF training subphase,initiator 102 sequentially transmits MIMO BF polling frames 1010 toindividual responders 104 in the group. Each MIMO BF polling frame 1010includes information indicating the number of TRN subfields to be usedfor receive AWV training in EDMG BRP-RX/TX packet 1012 subsequentlytransmitted by corresponding responder 104. Each responder 104 receivesMIMO BF polling frame 1010. Responder 104 corresponding to the addressincluded in MIMO BF polling frame 1010 transmits one or plural EDMGBRP-RX/TX packets 1012 to initiator 102.

On the basis of the number M of responders 104 in the group designatedby the EDMG group ID and the group user mask illustrated in FIG. 5,initiator 102 starts the MU-MIMO BF selection subphase after receivingthe last EDMG BRP-RX/TX packet from M-th responder 104 in the group,that is, last responder 104 in the group. In the MU-MIMO BF selectionsubphase, initiator 102 transmits one or plural MIMO BF selection frames1030 to individual responders 104 in the group. Each MIMO BF selectionframe includes information about an MU-MIMO transmission configuration.

<Flowchart>

FIG. 12 illustrates flowchart 1100 for setting the information fields ofMIMO setup control element 400 according to Embodiment 1. Flowchart 1100starts from step 1102. In step 1104, initiator 102 determines whetherSU-MIMO or MU-MIMO BF training is intended. In a case where SU-MIMO BFtraining is intended (Yes in step 1104), flowchart 1100 proceeds to step1110. Otherwise (No in step 1104), flowchart 1100 proceeds to step 1120.

In step 1110, the SU/MU field of MIMO setup control element 400 is setto 1 to indicate that SU-MIMO BF training is intended. In step 1120, theSU/MU field of MIMO setup control element 400 is set to 0 to indicatethat SU-MIMO BF training is not intended.

In step 1112, initiator 102 evaluates whether both initiator 102 andresponder 104 have antenna pattern reciprocity. In a case where bothinitiator 102 and responder 104 have antenna pattern reciprocity (Yes instep 1112), flowchart 1100 proceeds to step 1114. Otherwise (No in step1112), flowchart 1100 proceeds to step 1116.

In step 1116, the non-reciprocal/reciprocal SU-MIMO phase field of MIMOsetup control element 400 is set to 1 to indicate that thenon-reciprocal MIMO phase (see FIG. 2) is applied to SU-MIMO BFtraining. Subsequently, flowchart 1100 ends in step 1130.

In step 1114, initiator 102 determines whether the reciprocal MIMO phaseis intended to be applied to SU-MIMO BF training. In a case where thereciprocal MIMO phase is intended to be applied to SU-MIMO BF training(Yes in step 1114), the non-reciprocal/reciprocal SU-MIMO phase field ofMIMO setup control element 400 is set to 0 to indicate that thereciprocal MIMO phase (see FIG. 7) is applied to SU-MIMO BF training instep 1118, and subsequently flowchart 1100 ends in step 1130. In a casewhere the reciprocal MIMO phase is not intended to be applied to SU-MIMOBF training (No in step 1114), flowchart 1100 proceeds to step 1116.

In step 1120, the SU/MU field of MIMO setup control element 400 is setto 0. Subsequently, in step 1122, initiator 102 evaluates whetherinitiator 102 has antenna pattern reciprocity. In a case where initiator102 has antenna pattern reciprocity (Yes in step 1122), flowchart 1100proceeds to step 1124. Otherwise (No in step 1122), flowchart 1100proceeds to step 1126, where the DL/UL MU-MIMO phase field of MIMO setupcontrol element 400 is set to 1 to indicate that the downlink MIMO phase(see FIG. 10) is applied to MU-MIMO BF training. Subsequently, flowchart1100 ends in step 1130.

In step 1124, initiator 102 determines whether the uplink MIMO phase isintended to be applied to MU-MIMO BF training. In a case where theuplink MIMO phase is intended to be applied to MU-MIMO BF training (Yesin step 1124), flowchart 1100 proceeds to step 1128. Otherwise (No instep 1124), flowchart 1100 proceeds to step 1126.

In step 1128, the DL/UL MU-MIMO phase field of MIMO setup controlelement 400 is set to 0 to indicate that the uplink MIMO phase (see FIG.11) is applied to MU-MIMO BF training, and subsequently flowchart 1100ends in step 1130. Otherwise (No in step 1124), flowchart 1100 proceedsto step 1126.

FIG. 13 illustrates flowchart 1200 for interpreting the informationfields of MIMO setup control element 400 according to Embodiment 1.Flowchart 1200 starts from step 1202. In step 1204, responder 104 thathas received MIMO setup control element 400 checks whether the SU/MUfield is set to 1. In a case where the SU/MU field is set to 1 (Yes instep 1204), flowchart 1200 proceeds to step 1210. In a case where theSU/MU field is set to 0 (No in step 1204), flowchart 1200 proceeds tostep 1220.

In step 1210, responder 104 checks whether the non-reciprocal/reciprocalSU-MIMO phase field of received MIMO setup control element 400 is set to0. In a case where the non-reciprocal/reciprocal SU-MIMO phase field isset to 0 (Yes in step 1210), flowchart 1200 proceeds to step 1214. In acase where the non-reciprocal/reciprocal SU-MIMO phase field is set to 1(No in step 1210), flowchart 1200 proceeds to step 1212.

In step 1214, responder 104 determines that the reciprocal MIMO phase isapplied to SU-MIMO BF training, and flowchart 1200 ends in step 1230. Instep 1212, responder 104 determines that the non-reciprocal MIMO phaseis applied to SU-MIMO BF training, and flowchart 1200 ends in step 1230.

In step 1220, responder 104 checks whether the DL/UL MU-MIMO phase fieldof received MIMO setup control element 400 is set to 0. In a case wherethe DL/UL MU-MIMO phase field is set to 0 (Yes in step 1220), flowchart1200 proceeds to step 1224. In a case where the DL/UL MU-MIMO phasefield is set to 1 (No in step 1220), flowchart 1200 proceeds to step1222.

In step 1224, responder 104 determines that the uplink MIMO phase isapplied to MU-MIMO BF training, and flowchart 1200 ends in step 1230. Instep 1222, responder 104 determines that the downlink MIMO phase isapplied to MU-MIMO BF training, and flowchart 1200 ends in step 1230.

According to Embodiment 1, with use of a condition in which bothinitiator 102 and responder 104 have antenna pattern reciprocity, theR-SMBT subphase is omitted and the SU-MIMO BF feedback subphase issimplified. Accordingly, the time required for SU-MIMO BF training canbe reduced compared with the non-reciprocal MIMO phase illustrated inFIG. 2.

In addition, according to Embodiment 1, even in a case where thereciprocal MIMO phase is applied to SU-MIMO BF training, initiator 102may determine an appropriate transmission parameter, for example, a MCS,to be used for communication with responder 104 that has transmittedMIMO BF feedback 922 illustrated in FIG. 10, on the basis of MIMOchannel quality information included in MIMO BF feedback 922, forexample, the SNR. In addition, initiator 102 may determine anappropriate transmission parameter, for example, a MCS, to be used forcommunication with responder 104 that has transmitted BRP frame 1012illustrated in FIG. 11, in accordance with the reception quality of BRPframe 1012. In this way, initiator 102 is capable of determining anappropriate transmission parameter, for example, a MCS, to be used forcommunication with responder 104 after the digital BF procedure has beenexecuted. In the reciprocal MIMO phase, initiator 102 may omit notifyingresponder 104 of information about receive sectors, and thus the timerequired for SU-MIMO BF training can be reduced.

In addition, according to Embodiment 1, it is understood that, in a casewhere initiator 102 has antenna pattern reciprocity, the MU-MIMO BFfeedback subphase is omitted in the uplink MIMO phase illustrated inFIG. 11, compared with the downlink MIMO phase illustrated in FIG. 10.As a result of the MU-MIMO BF feedback subphase being omitted, the timerequired for MU-MIMO BF training can be reduced.

[Modification Example 1]

In Embodiment 1 described above, in the digital BF procedure illustratedin FIG. 8A or FIG. 8B, responder 104 determines an appropriate MCS to beused by responder 104 on the basis of MIMO BF feedback frame 714transmitted by responder 104 in response to EDMG BRP-TX packet 712transmitted by initiator 102. In contrast to this, in ModificationExample 1, an opportunity to transmit feedback of the SNR for theresponder link is acquired so that responder 104 is capable ofdetermining an appropriate MCS on the basis of the SNR even in a casewhere the digital BF procedure cannot be used.

FIG. 14 illustrates a reciprocal MIMO phase of SU-MIMO BF trainingaccording to Modification Example 1. In one example, TRN field 624 isadded to MIMO BF feedback frame 622 that is transmitted by responder 104to transmit feedback of the SNR, as illustrated in FIG. 14.

TRN field 624 is determined on the basis of recommended TX/RX sectorcombinations for the initiator link, and is transmitted by responder 104by using recommended RX/TX sector combinations for the responder link.In one example, one or plural TRN units that are at the head of TRNfield 624, that are added to MIMO BF feedback frame 622, and that cannotbe processed by initiator 102 may be used by initiator 102 to switch theantenna configuration on the basis of the recommended RX/TX sectorcombinations for the responder link.

Subsequently, initiator 102 transmits MIMO BF feedback frame 626 (athird MIMO BF feedback frame) including feedback of the SNR for theresponder link.

MIMO BF setup frame 602, MIMO BF setup frame 604, and EDMG BRP-RX/TXpackets 610 illustrated in FIG. 14 are similar to those illustrated inFIG. 7, and the description thereof is omitted.

According to Modification Example 1, even in a case where hybrid BFcannot be used, responder 104 is capable of determining an appropriateMCS to be used by responder 104 on the basis of feedback of the SNR forthe responder link included in MIMO BF feedback frame 626. In Embodiment1, appropriate MCSs to be used by initiator 102 and responder 104 aredetermined through the SU-MIMO BF training illustrated in FIG. 7 and thedigital BF procedure illustrated in FIG. 8A or FIG. 8B. In contrast tothis, in Modification Example 1, appropriate MCSs to be used byinitiator 102 and responder 104 can be determined through the SU-MIMO BFtraining illustrated in FIG. 14. Initiator 102 may measure digital BFinstead of measuring the SNR of the responder link, by using TRN field624 illustrated in FIG. 14.

[Modification Example 2]

In Modification Example 1 described above, responder 104 determines anappropriate MCS to be used by responder 104 on the basis of feedback ofthe SNR for the responder link transmitted by initiator 102.Alternatively, in Modification Example 2, responder 104 determines anappropriate MCS to be used by responder 104 on the basis of informationindicating a transmission power transmitted by initiator 102.

FIG. 15 illustrates a reciprocal MIMO phase of SU-MIMO BF trainingaccording to Modification Example 2. As illustrated in FIG. 15, forexample, MIMO BF setup frame 602 transmitted by initiator 102 includestransmission EIRP field 602 a indicating a transmission equivalentisotropic radiated power (EIRP) of initiator 102. Field 602 a indicatingthe transmission EIRP may be inserted after, for example, thenon-reciprocal/reciprocal SU-MIMO phase field of MIMO setup controlelement 400 illustrated in FIG. 5.

With use of a value P_(I, TX) of the transmission EIRP indicated intransmission EIRP field 602 a, responder 104 is capable of calculating avalue RSSI_(I) of RSSI of initiator 102 by using the following equation.

RSSI_(I) =P _(R, TX) −P _(I, TX)+RSSI_(R)

Here, P_(I, TX) represents the value of the transmission EIRP ofresponder 104, and RSSI_(R) represents the value of RSSI of responder104. The values of P_(I, TX) and RSSI_(R) are known to responder 104.

Subsequently, responder 104 is capable of determining an appropriate MCSto be used by responder 104 on the basis of the calculated value ofRSSI_(I).

MIMO BF setup frame 604, EDMG BRP-RX/TX packets 610, and MIMO BFfeedback frame 622 illustrated in FIG. 15 are similar to thoseillustrated in FIG. 7, and the description thereof is omitted.

According to Modification Example 2, even in a case where hybrid BFcannot be used, responder 104 is capable of determining an appropriateMCS to be used by responder 104 on the basis of the transmission EIRP ofinitiator 102. In Embodiment 1, appropriate MCSs to be used by initiator102 and responder 104 are determined through the SU-MIMO BF trainingillustrated in FIG. 7 and the digital BF procedure illustrated in FIG.8A or FIG. 8B. In contrast to this, in Modification Example 2,appropriate MCSs to be used by initiator 102 and responder 104 can bedetermined through the SU-MIMO BF training illustrated in FIG. 15.

[Modification Example 3]

In Modification Example 3, a case is considered in which both initiator102 and responder 104 have antenna pattern reciprocity. In ModificationExample 3, transmission and reception of frames or packets correspondingto MIMO BF setup frame 204, I-SMBT, and MIMO BF feedback 234 among theframes illustrated in FIG. 2 transmitted and received in thenon-reciprocal MIMO phase are omitted.

FIG. 16 illustrates a reciprocal MIMO phase of SU-MIMO BF trainingaccording to Modification Example 3. The reciprocal MIMO phase ofModification Example 3 is formed of three subphases, an SU-MIMO BF setupsubphase, an R-SMBT subphase, and an SU-MIMO BF feedback subphase. Inthe reciprocal MIMO phase of Modification Example 3, transmission andreception of frames or packets corresponding to MIMO BF setup frame 204,I-SMBT for the responder link, and MIMO BF feedback 234 for I-SMBT amongthe frames illustrated in FIG. 2 transmitted and received in thenon-reciprocal MIMO phase can be omitted.

In the SU-MIMO BF setup subphase, initiator 102 transmits MIMO BF setupframe 652 to responder 104. In Modification Example 3, the values of theSU/MU field and the non-reciprocal/reciprocal SU-MIMO phase field of theMIMO setup control element in MIMO BF setup frame 652 are set to 1 and0, respectively, to indicate that the reciprocal MIMO phase is appliedto SU-MIMO BF training. The value of the link type field is set to 0 toindicate that the configuration information included in MIMO BF setupframe 652 is about the responder link.

Subsequently, responder 104 starts the R-SMBT subphase. In the R-SMBTsubphase, responder 104 transmits EDMG BRP-RX/TX packets 660 (a thirdBRP packet) to initiator 102. The number of TRN subfields of each EDMGBRP-RX/TX packet 660 is configured in accordance with the TRNconfiguration information in MIMO BF setup frame 652 received frominitiator 102 in the SU-MIMO BF setup subphase.

After receiving last EDMG BRP-RX/TX packet 662 from responder 104,initiator 102 starts the SU-MIMO BF feedback subphase. Initiator 102transmits MIMO BF feedback frame 672 to responder 104. MIMO BF feedbackframe 672 includes information indicating a recommended TX sectorcombination for the responder link determined on the basis of channelmeasurement data acquired from the R-SMBT subphase, and informationindicating the SNR corresponding to the recommended TX sectorcombination. In addition, MIMO BF feedback frame 672 may includeinformation indicating a channel measurement result corresponding to therecommended TX sector combination.

In Modification Example 3, in the reciprocal MIMO phase of SU-MIMO BFtraining illustrated in FIG. 16, recommended RX/TX sector combinationsdetermined for the responder link, that is, recommended RX/TX sectorcombinations, are handled as recommended TX/RX sector combinations forthe initiator link.

On the basis of the recommended TX/RX sector combinations for theinitiator link, initiator 102 determines a recommended TX sectorcombination to be used by initiator 102 for the initiator link. Therecommended TX sector combination to be used by initiator 102 for theinitiator link may be the same as the recommended RX sector combinationto be used by initiator 102 for the responder link.

On the basis of the recommended TX/RX sector combinations for theinitiator link, responder 104 determines a recommended RX sectorcombination to be used by responder 104 for the initiator link. Therecommended RX sector combination to be used by responder 104 for theinitiator link may be the same as the recommended TX sector combinationto be used by responder 104 for the responder link.

In Embodiment 1, appropriate MCSs to be used by initiator 102 andresponder 104 are determined through the SU-MIMO BF training illustratedin FIG. 7 and the digital BF procedure illustrated in FIG. 8A or FIG.8B. In contrast to this, in Modification Example 3, appropriate MCSs tobe used by initiator 102 and responder 104 can be determined through theSU-MIMO BF training illustrated in FIG. 16.

According to Modification Example 3, with use of a condition in whichboth initiator 102 and responder 104 have antenna pattern reciprocity,the I-SMBT subphase is omitted and the SU-MIMO BF setup subphase and theSU-MIMO BF feedback subphase are simplified. Accordingly, the timerequired for SU-MIMO BF training can be reduced compared with thenon-reciprocal MIMO phase illustrated in FIG. 2.

In addition, in Embodiment 1, two MIMO BF setup frames 602 and 604 aretransmitted and received in a two-way manner in the SU-MIMO BF setupphase as illustrated in FIG. 7. In contrast to this, in ModificationExample 3, one MIMO BF setup frame 652 is transmitted and received in aone-way manner in the SU-MIMO BF setup phase as illustrated in FIG. 16.Thus, in the SU-MIMO BF setup phase in Modification Example 3, theexecution time can be shortened compared with the SU-MIMO BF setup phasein Embodiment 1.

FIG. 17 illustrates an example of a digital BF procedure according toModification Example 3. In Embodiment 1, digital BF is applied to theresponder link. In contrast to this, in Modification Example 3, digitalBF is applied to the initiator link. In Embodiment 1, the SU-MIMO BFtraining (analog BF procedure) illustrated in FIG. 7 is performed andthen the digital BF procedure illustrated in FIG. 8A or FIG. 8B isperformed. In contrast to this, in Modification Example 3, the analog BFprocedure illustrated in FIG. 16 is performed and then the digital BFprocedure illustrated in FIG. 17 is performed.

First, initiator 102 transmits CT 702 a and grant frame 702 to responder104. Here, CT 702 a indicates the antenna configuration used for theinitiator link in the digital BF procedure.

Subsequently, after successfully receiving grant frame 702, responder104 transmits CT 704 a and grant ack frame 704 to respond to initiator102. Here, CT 704 a indicates the antenna configuration used for theresponder link in the digital BF procedure.

Subsequently, initiator 102 transmits CT 706 a and RTS frame 706 toresponder 104 to access a channel, and makes a notification about thestart of the digital BF procedure for the responder link. Here, CT 706 aindicates the antenna configuration used for the initiator link in thedigital BF procedure.

Subsequently, after successfully receiving RTS frame 706, responder 104transmits CT 708 a and DMG CTS frame 708 to respond to initiator 102.Here, CT 708 a includes information indicating the antenna configurationused for the responder link in the digital BF procedure. Furthermore,initiator 102 configures array antennas for the initiator link on thebasis of the antenna configuration information in grant frame 702.

Subsequently, initiator 102 transmits EDMG BRP-TX packet 722 (a fourthBRP packet) illustrated in FIG. 17, thereby sounding a channel for theinitiator link. EDMG BRP-TX packet 722 is transmitted with the antennaconfiguration for the initiator link based on the result of the SU-MIMOBF training illustrated in FIG. 16.

Subsequently, responder 104 transmits MIMO BF feedback frame 724 (afourth MIMO BF feedback frame) including the SNR, MIMO channelmeasurement, or digital precoding matrix information for the initiatorlink, to respond to initiator 102.

In Embodiment 1, BRP frame 612 is transmitted in the initiator link inthe analog BF procedure, and BRP frame 712 is transmitted in theresponder link in the digital BF procedure. In contrast to this, inModification Example 3, BRP frame 662 is transmitted in the responderlink in the analog BF procedure, and BRP frame 722 is transmitted in theinitiator link in the digital BF procedure. In Modification Example 3,as in Embodiment 1, BRP frames are transmitted in directions reverse toeach other in the analog BF procedure and the digital BF procedure.Accordingly, even in a case where I-SMBT or R-SMBT is omitted, the SNRsof the respective links can be measured.

As a result of the above-described procedure, initiator 102 obtainsfeedback of the SNR for the initiator link by using hybrid BF anddetermines an appropriate MCS on the basis of the SNR.

In this way, even in a case where the reciprocal MIMO phase is appliedto SU-MIMO BF training, initiator 102 is capable of determining anappropriate transmission parameter for the initiator link, for example,a MCS, after the digital BF procedure has been executed.

According to Modification Example 3, in the reciprocal MIMO phase,responder 104 may omit notifying initiator 102 of information aboutreceive sectors, and thus the time required for SU-MIMO BF training canbe reduced.

Modification Example 1 and Modification Example 3 may be combined toproduce Modification Example 4. In Modification Example 4, a TRN fieldis added to MIMO BF feedback frame 672 illustrated in FIG. 16, and MIMOBF feedback frame 672 and the TRN field are transmitted by initiator 102by using recommended RX/TX sector combinations for the initiator link.The recommended RX/TX sector combinations for the initiator link aredetermined on the basis of recommended TX/RX sector combinations for theresponder link. (See FIG. 14. Note that, in FIG. 14, responder 104transmits TRN field 624.)

Subsequently, responder 104 transmits a MIMO BF feedback frame includingfeedback of the SNR for the initiator link. (See FIG. 14. Note that, inFIG. 14, initiator 102 transmits MIMO BF feedback frame 626.)

According to Modification Example 4, even in a case where hybrid BFcannot be used, initiator 102 is capable of determining an appropriateMCS to be used by initiator 102 on the basis of the SNR of the initiatorlink.

Embodiment 2

In Embodiment 2, the downlink MIMO phase in MU-MIMO BF (see FIG. 10) isreferred to as a non-reciprocal MIMO phase. On the other hand, theuplink MIMO phase (see FIG. 11) is referred to as a reciprocal MIMOphase because the uplink MIMO phase uses the antenna pattern reciprocityof initiator 102.

FIG. 18 illustrates an example of a format of MIMO setup control element1300 according to Embodiment 2. MIMO setup control element 1300 includesan SU/MU field, a non-reciprocal/reciprocal MIMO phase field, and aninitiator field. The SU/MU field indicates whether SU-MIMO or MU-MIMO BFis applied. The non-reciprocal/reciprocal MIMO phase field indicateswhich of a non-reciprocal MIMO phase and a reciprocal MIMO phase isapplied to SU-MIMO BF training or MU-MIMO BF training. The initiatorfield indicates which of initiator 102 and responder 104 is thetransmission source of MIMO setup control element 1300.

Initiator 102 may transmit MIMO setup control element 1300 by includingit in MIMO BF setup frame 602, 902, 1002, or 652. Responder 104 maytransmit MIMO setup control element 1300 by including it in MIMO BFsetup frame 604.

In Embodiment 2, the initiator field is used, instead of the link typefield in Embodiment 1, in the MIMO setup control element.

As described above, the link type field in FIG. 5 indicates whetherconfiguration information is information about the initiator link orinformation about the responder link. In contrast to this, MIMO setupcontrol element 1300 includes information about both the initiator linkand the responder link, information about the initiator link, andinformation about the responder link. This will be described.

The information about both the initiator link and the responder linkincludes, for example, information on the SU/MU field, an EDMG group IDfield, and a group user mask field. The SU/MU field indicates which ofSU-MIMO BF and MU-MIMO BF is to be executed, and is thus informationabout both the initiator link and the responder link. In the case ofMU-MIMO BF, the IDs of communication devices that participate in MU-MIMOBF are determined by combining the EDMG group ID field and the groupuser mask field.

In a case where MIMO setup control element 1300 is transmitted byinitiator 102, the information about the initiator link includes, forexample, information on a MIMO FBCK-REQ field and a transmission powerfield. The MIMO FBCK-REQ field indicates channel measurement feedbackrequested for the initiator link. The transmission power field indicatesthe transmission power of the initiator link. In a case where MIMO setupcontrol element 1300 is transmitted by responder 104, each fieldindicates information about the responder link.

In a case where MIMO setup control element 1300 is transmitted byinitiator 102, the information about the responder link includes, forexample, information on an L-TX-RX field and a requested EDMG TRN unit Mfield. The L-TX-RX field and the requested EDMG TRN unit M fieldindicate the number of TRN subfields requested for receive AWV trainingfor the responder link. In a case where MIMO setup control element 1300is transmitted by responder 104, each field indicates information aboutthe initiator link.

Initiator 102 includes, in MIMO setup control element 1300, an initiatorfield indicating which of initiator 102 and responder 104 is atransmitter of MIMO setup control element 1300. Responder 104 that hasreceived MIMO setup control element 1300 is capable of determining, byusing the value indicated by the initiator field, which of theinformation about both the initiator link and the responder link, theinformation about the initiator link, and the information about theresponder link is the configuration information (information in eachfield) of MIMO setup control element 1300.

The initiator field is included in MIMO setup control element 1300 alsoin a case where responder 104 transmits MIMO setup control element 1300.Thus, responder 104 is capable of discriminating the configurationinformation (information in each field) of MIMO setup control element1300 by using the value indicated by the initiator field.

In Embodiment 2, the SU/MU field and the non-reciprocal/reciprocal MIMOphase field in the format of MIMO setup control element 1300 in FIG. 18indicate which of the non-reciprocal MIMO phase of SU-MIMO BF trainingillustrated in FIG. 2, the reciprocal MIMO phase of SU-MIMO BF trainingillustrated in FIG. 7, the non-reciprocal MIMO phase of MU-MIMO BFtraining illustrated in FIG. 10, and the reciprocal MIMO phase ofMU-MIMO BF training illustrated in FIG. 11 is to be used.

In the case of executing the non-reciprocal MIMO phase of SU-MIMO BFtraining illustrated in FIG. 2, both the SU/MU field and thenon-reciprocal/reciprocal MIMO phase field of MIMO setup control element1300 in MIMO BF setup frame 202 or MIMO BF setup frame 204 are set to 0to indicate that the non-reciprocal MIMO phase is applied to SU-MIMO BFtraining. The initiator field of MIMO setup control element 1300 in MIMOBF setup frame 202 is set to 1 to indicate that the transmission sourceof MIMO BF setup frame 202 is initiator 102. The initiator field of MIMOsetup control element 1300 in MIMO BF setup frame 204 is set to 0 toindicate that the transmission source of MIMO BF setup frame 204 isresponder 104.

In the case of executing the reciprocal MIMO phase of SU-MIMO BFtraining illustrated in FIG. 7, both the SU/MU field and thenon-reciprocal/reciprocal MIMO phase field of MIMO setup control element1300 in MIMO BF setup frame 602 or MIMO BF setup frame 604 are set to 0and 1, respectively, to indicate that the reciprocal MIMO phase isapplied to SU-MIMO BF training. The initiator field of MIMO setupcontrol element 1300 in MIMO BF setup frame 602 is set to 1 to indicatethat the transmission source of MIMO BF setup frame 602 is initiator102. The initiator field of MIMO setup control element 1300 in MIMO BFsetup frame 604 is set to 0 to indicate that the transmission source ofMIMO BF setup frame 604 is responder 104.

In the case of executing the non-reciprocal MIMO phase of MU-MIMO BFtraining illustrated in FIG. 10, both the SU/MU field and thenon-reciprocal/reciprocal MIMO phase field of MIMO setup control element1300 in MIMO BF setup frame 902 are set to 1 and 0, respectively, toindicate that the non-reciprocal MIMO phase is applied to MU-MIMO BFtraining. The initiator field of MIMO setup control element 1300 in

MIMO BF setup frame 902 is set to 1 to indicate that the transmissionsource of MIMO BF setup frame 902 is initiator 102.

In the case of executing the reciprocal MIMO phase of MU-MIMO BFtraining illustrated in FIG. 11, both the SU/MU field and thenon-reciprocal/reciprocal MIMO phase field of MIMO setup control element1300 in MIMO BF setup frame 1002 are set to 1 to indicate that thereciprocal MIMO phase is applied to MU-MIMO BF training. The initiatorfield of MIMO setup control element 1300 in MIMO BF setup frame 1002 isset to 1 to indicate that the transmission source of MIMO BF setup frame1002 is initiator 102.

<Flowchart>

FIG. 19 illustrates flowchart 1400 for setting the information fields ofMIMO setup control element 1300 according to Embodiment 2. Flowchart1400 starts from step 1402. In step 1404, initiator 102 determineswhether SU-MIMO or MU-MIMO BF training is intended. In a case whereSU-MIMO BF training is intended (Yes in step 1404), flowchart 1400proceeds to step 1410. Otherwise (No in step 1404), flowchart 1400proceeds to step 1420.

In step 1410, the SU/MU field of MIMO setup control element 1300 is setto 0 to indicate that SU-MIMO BF training is intended.

In step 1412, initiator 102 evaluates whether both initiator 102 andresponder 104 have antenna pattern reciprocity. In a case where bothinitiator 102 and responder 104 have antenna pattern reciprocity (Yes instep 1412), flowchart 1400 proceeds to step 1414. Otherwise (No in step1412), flowchart 1400 proceeds to step 1416.

In step 1416, the non-reciprocal/reciprocal MIMO phase field of MIMOsetup control element 1300 is set to 0 to indicate that thenon-reciprocal MIMO phase (see FIG. 2) is applied to SU-MIMO BFtraining. Subsequently, flowchart 1400 ends in step 1430.

In step 1414, initiator 102 determines whether the reciprocal MIMO phaseis intended to be applied to SU-MIMO BF training. In a case where thereciprocal MIMO phase is intended to be applied to SU-MIMO BF training(Yes in step 1414), flowchart 1400 proceeds to step 1418. Otherwise (Noin step 1414), flowchart 1400 proceeds to step 1416.

In step 1418, the non-reciprocal/reciprocal MIMO phase field of MIMOsetup control element 1300 is set to 1 to indicate that the reciprocalMIMO phase (see FIG. 7) is applied to SU-MIMO BF training, andsubsequently flowchart 1400 ends in step 1430.

In step 1420, the SU/MU field of MIMO setup control element 1300 is setto 1 to indicate that MU-MIMO BF training is intended.

In step 1422, initiator 102 evaluates whether initiator 102 has antennapattern reciprocity. In a case where initiator 102 has antenna patternreciprocity (Yes in step 1422), flowchart 1400 proceeds to step 1424.Otherwise (No in step 1422), flowchart 1400 proceeds to step 1426.

In step 1426, the non-reciprocal/reciprocal MIMO phase field of MIMOsetup control element 1300 is set to 0 to indicate that thenon-reciprocal MIMO phase (see FIG. 10) is applied to MU-MIMO BFtraining. Subsequently, flowchart 1400 ends in step 1430.

In step 1424, initiator 102 determines whether the reciprocal MIMO phaseis intended to be applied to MU-MIMO BF training. In a case where thereciprocal MIMO phase is intended to be applied to MU-MIMO BF training(Yes in step 1424), flowchart 1400 proceeds to step 1428. Otherwise (Noin step 1424), flowchart 1400 proceeds to step 1426.

In step 1428, the non-reciprocal/reciprocal MIMO phase field of MIMOsetup control element 1300 is set to 1 to indicate that the reciprocalMIMO phase (see FIG. 11) is applied to MU-MIMO BF training, andsubsequently flowchart 1400 ends in step 1430.

FIG. 20 illustrates flowchart 1500 for interpreting the informationfields of MIMO setup control element 1300 according to Embodiment 2.Flowchart 1500 starts from step 1502. In step 1504, responder 104 thathas received MIMO setup control element 1300 checks whether the SU/MUfield is set to 0. In a case where the SU/MU field is set to 0 (Yes instep 1504), flowchart 1500 proceeds to step 1510. Otherwise (No in step1504), flowchart 1500 proceeds to step 1520.

In step 1510, responder 104 checks whether the non-reciprocal/reciprocalMIMO phase field of received MIMO setup control element 1300 is setto 1. In a case where the non-reciprocal/reciprocal MIMO phase field isset to 1 (Yes in step 1510), flowchart 1500 proceeds to step 1514.Otherwise (No in step 1510), flowchart 1500 proceeds to step 1512.

In step 1514, responder 104 determines that the reciprocal MIMO phase isapplied to SU-MIMO BF training, and flowchart 1500 ends in step 1530. Instep 1512, responder 104 determines that non-reciprocal MIMO phase isapplied to SU-MIMO BF training, and flowchart 1500 ends in step 1530.

In step 1520, responder 104 checks whether the non-reciprocal/reciprocalMIMO phase field of received MIMO setup control element 1300 is setto 1. In a case where the non-reciprocal/reciprocal MIMO phase field isset to 1 (Yes in step 1520), flowchart 1500 proceeds to step 1524.Otherwise (No in step 1520), flowchart 1500 proceeds to step 1522.

In step 1524, responder 104 determines that the reciprocal MIMO phase isapplied to MU-MIMO BF training, and flowchart 1500 ends in step 1530. Instep 1522, responder 104 determines that the non-reciprocal MIMO phaseis applied to MU-MIMO BF training, and flowchart 1500 ends in step 1530.

According to Embodiment 2, one signal transmission bit in a MIMO setupcontrol element can be saved compared with Embodiment 1.

The present disclosure can be realized by software, hardware, orsoftware in cooperation with hardware. Each functional block used in thedescription of each embodiment described above can be partly or entirelyrealized by an LSI such as an integrated circuit, and each processdescribed in the each embodiment may be controlled partly or entirely bythe same LSI or a combination of LSIs. The LSI may be individuallyformed as chips, or one chip may be formed so as to include a part orall of the functional blocks. The LSI may include a data input andoutput coupled thereto. The LSI here may be referred to as an IC, asystem LSI, a super LSI, or an ultra LSI depending on a difference inthe degree of integration. However, the technique of implementing anintegrated circuit is not limited to the LSI and may be realized byusing a dedicated circuit, a general-purpose processor, or aspecial-purpose processor. In addition, a FPGA (Field Programmable GateArray) that can be programmed after the manufacture of the LSI or areconfigurable processor in which the connections and the settings ofcircuit cells disposed inside the LSI can be reconfigured may be used.The present disclosure can be realized as digital processing or analogueprocessing. If future integrated circuit technology replaces LSIs as aresult of the advancement of semiconductor technology or otherderivative technology, the functional blocks could be integrated usingthe future integrated circuit technology. Biotechnology can also beapplied.

A communication system according to the present disclosure (an initiatordevice and a responder device) can be used for communication betweenvehicles, communication between a road and a vehicle, communicationbetween a vehicle and a store, communication between a train and astation platform, and communication between an aircraft and a boardingbridge (passenger step).

An initiator device according to the present disclosure is a device thatsupports a single user (SU)-multiple input multiple output (MIMO)operation, including: a generation circuit that generates a first signalincluding a value indicating which of a reciprocal MIMO phase and anon-reciprocal MIMO phase is applied to SU-MIMO beamforming (BF)training; and a transmission circuit that transmits the first signal toa responder device.

In the initiator device according to the present disclosure, in a casewhere both the initiator device and the responder device have antennapattern reciprocity, the first signal includes a value indicating thatthe reciprocal MIMO phase is applied to the SU-MIMO BF training.

In the initiator device according to the present disclosure, the firstsignal is a MIMO BF setup frame.

The initiator device according to the present disclosure includes: areception circuit; and a control circuit, in which, in a case where thereciprocal MIMO phase is applied to the SU-MIMO BF training, thetransmission circuit transmits to the responder device a first beamrefinement protocol (BRP) signal for training transmit sectors that areto be used for MIMO transmission by the initiator device, the receptioncircuit receives from the responder device a first MIMO BF feedbacksignal including feedback information for the first BRP signal, and thecontrol circuit determines, on the basis of the feedback information forthe first BRP signal, a transmit sector combination and a receive sectorcombination that are to be used for MIMO transmission by the initiatordevice.

In the initiator device according to the present disclosure, in adigital BF procedure of a hybrid BF operation that is performed afterthe SU-MIMO BF training, the reception circuit receives from theresponder device a second BRP signal for training a transmit sectorcombination that is to be used for MIMO transmission by the responderdevice, and the transmission circuit transmits to the responder device asecond MIMO BF feedback signal including feedback information for thesecond BRP signal.

In the initiator device according to the present disclosure, thereception circuit receives from the responder device a training (TRN)signal for training a transmit sector combination that is to be used forMIMO transmission by the responder device, the TRN signal being added tothe first MIMO BF feedback signal, and the transmission circuittransmits to the responder device a third MIMO BF feedback signalincluding feedback information for the TRN signal.

In the initiator device according to the present disclosure, the firstsignal includes information indicating a transmission power of thetransmit sector combination.

In the initiator device according to the present disclosure, in a casewhere the reciprocal MIMO phase is applied to the SU-MIMO BF training,the reception circuit receives from the responder device a third BRPsignal for training a transmit sector combination that is to be used forMIMO transmission by the responder device, the transmission circuittransmits to the responder device a third MIMO BF feedback signalincluding feedback information for the third BRP signal, and the controlcircuit determines, on the basis of the third BRP signal, a transmitsector combination and a receive sector combination that are to be usedfor MIMO transmission by the initiator device.

In the initiator device according to the present disclosure, in adigital BF procedure of a hybrid BF operation that is performed afterthe SU-MIMO BF training, the reception circuit receives from theresponder device a fourth BRP signal with which the responder devicesounds a channel for a responder link, and the transmission circuittransmits to the responder device a fourth MIMO BF feedback signalincluding feedback information for the fourth BRP signal.

A responder device according to the present disclosure is a device thatsupports a single user (SU)-multiple input multiple output (MIMO)operation, including: a reception circuit that receives from aninitiator device a first signal including a value indicating which of areciprocal MIMO phase and a non-reciprocal MIMO phase is applied toSU-MIMO beamforming (BF) training; and a processing circuit thatdetermines, on the basis of the value, which of the reciprocal MIMOphase and the non-reciprocal MIMO phase is applied to the SU-MIMO BFtraining.

In the responder device according to the present disclosure, the firstsignal is a MIMO BF setup signal.

The responder device according to the present disclosure includes: atransmission circuit; and a control circuit, in which, in a case wherethe processing circuit determines that the reciprocal MIMO phase isapplied to the SU-MIMO BF training, the reception circuit receives fromthe initiator device a first beam refinement protocol (BRP) signal fortraining a transmit sector combination that is to be used for MIMOtransmission by the initiator device, the transmission circuit transmitsto the initiator device a first MIMO BF feedback signal includingfeedback information for the first BRP signal, and the control circuitdetermines, on the basis of the first BRP signal, a transmit sectorcombination and a receive sector combination that are to be used forMIMO transmission by the responder device.

In the responder device according to the present disclosure, in adigital BF procedure of a hybrid BF operation that is performed afterthe SU-MIMO BF training, the transmission circuit transmits to theinitiator device a second BRP signal for training a transmit sectorcombination that is to be used for MIMO transmission by the responderdevice, the reception circuit receives from the initiator device asecond MIMO BF feedback signal including feedback information for thesecond BRP signal, and the control circuit determines, on the basis ofthe feedback information for the second BRP signal, a modulation andcoding scheme for MIMO transmission by the responder device.

In the responder device according to the present disclosure, thetransmission circuit transmits to the initiator device a training (TRN)signal for training a transmit sector combination that is to be used forMIMO transmission by the responder device, the TRN signal being added tothe first MIMO BF feedback signal, the reception circuit receives fromthe responder device a third MIMO BF feedback signal including feedbackinformation for the TRN signal, and the control circuit determines, onthe basis of the feedback information for the TRN signal, a modulationand coding scheme for MIMO transmission by the responder device.

In the responder device according to the present disclosure, the firstsignal includes information indicating a transmission power of thetransmit sector combination, and the control circuit determines, on thebasis of the information indicating the transmission power, a modulationand coding scheme for MIMO transmission by the responder device.

In the responder device according to the present disclosure, in a casewhere the processing circuit determines that the reciprocal MIMO phaseis applied to the SU-MIMO BF training, the transmission circuittransmits to the initiator device a third BRP signal for training atransmit sector combination that is to be used for MIMO transmission bythe responder device, the reception circuit receives from the responderdevice a third MIMO BF feedback signal including feedback informationfor the third BRP signal, and the control circuit determines, on thebasis of the feedback information for the third BRP signal, a transmitsector combination and a receive sector combination that are to be usedfor MIMO transmission by the responder device.

In the responder device according to the present disclosure, in adigital BF procedure of a hybrid BF operation that is performed afterthe SU-MIMO BF training, the transmission circuit transmits to theinitiator device a fourth BRP signal with which the responder devicesounds a channel for a responder link, the reception circuit receivesfrom the initiator device a fourth MIMO BF feedback signal includingfeedback information for the fourth BRP signal, and the control circuitdetermines, on the basis of the feedback information for the fourth BRPsignal, a modulation and coding scheme for MIMO transmission by theresponder device.

A system according to the present disclosure includes: an initiatordevice and a responder device that support a single user (SU)-multipleinput multiple output (MIMO) operation, in which the initiator deviceincludes a generation circuit that generates a first signal including avalue indicating which of a reciprocal MIMO phase and a non-reciprocalMIMO phase is applied to SU-MIMO beamforming (BF) training, and atransmission circuit that transmits the first signal to the responderdevice, and in which the responder device includes a reception circuitthat receives the first signal from the initiator device, and aprocessing circuit that determines, on the basis of the value, which ofthe reciprocal MIMO phase and the non-reciprocal MIMO phase is appliedto the SU-MIMO BF training.

This patent application claims priority based on U.S. Provisional PatentApplication No. 62/575,264 filed on Oct. 20, 2017, U.S. ProvisionalPatent Application No. 62/628,199 filed on Feb. 8, 2018, and JapanesePatent Application No. 2018-172815 filed on Sep. 14, 2018, which arehereby incorporated by reference herein in their entirety.

INDUSTRIAL APPLICABILITY

The present disclosure is useful for a multi-user wireless communicationsystem.

REFERENCE SIGNS LIST

-   800 STA-   810 Transmission signal generation circuit-   812 Message generation circuit-   820 Transceiver-   822 PHY processing circuit-   824 Antenna-   830 Received signal processing circuit-   832 Message processing circuit-   840 Control circuit-   842 BF control circuit

1. An initiator device that supports a single user (SU)-multiple inputmultiple output (MIMO) operation, comprising: a generation circuit thatgenerates a MIMO beamforming (BF) setup frame including anon-reciprocal/reciprocal MIMO phase field that indicates which of anon-reciprocal MIMO phase or a reciprocal MIMO phase is applied toSU-MIMO BF training; and a transmission circuit that transmits the MIMOBF setup frame to a responder device and that, in response to thenon-reciprocal/reciprocal MIMO phase field indicating that thereciprocal MIMO phase is applied, transmits to the responder device aplurality of first beam refinement protocol (BRP) signals for trainingtransmit sectors that are to be used for MIMO transmission by theinitiator device; and a reception circuit that receives from theresponder device a first MIMO BF feedback frame including feedbackinformation for the plurality of first BRP signals.
 2. The initiatordevice according to claim 1, wherein in response to the initiator deviceand the responder device having antenna pattern reciprocity, thenon-reciprocal/reciprocal MIMO phase field included in the MIMO BF setupframe is set to a first value indicating that the reciprocal MIMO phaseis applied to the SU-MIMO BF training.
 3. (canceled)
 4. The initiatordevice according to claim 1, comprising: a control circuit thatdetermines, on the basis of the feedback information for the pluralityof first BRP signals, a transmit sector combination and a receive sectorcombination for an initiator link.
 5. The initiator device according toclaim 4, wherein in a digital BF procedure of a hybrid BF operation thatis performed after the SU-MIMO BF training, the reception circuitreceives from the responder device a plurality of second BRP signals fortraining a transmit sector combination that is to be used for MIMOtransmission by the responder device, and the transmission circuittransmits to the responder device a second MIMO BF feedback frameincluding feedback information for the plurality of second BRP signals.6. The initiator device according to claim 4, wherein the receptioncircuit receives from the responder device a training (TRN) signal fortraining a transmit sector combination that is to be used for MIMOtransmission by the responder device, the TRN signal being added to thefirst MIMO BF feedback frame, and the transmission circuit transmits tothe responder device a third MIMO BF feedback frame including feedbackinformation for the TRN signal.
 7. (canceled)
 8. The initiator deviceaccording to claim 4, wherein in response to thenon-reciprocal/reciprocal MIMO phase field indicating that thereciprocal MIMO phase is applied to the SU-MIMO BF training, thereception circuit receives from the responder device a plurality ofthird BRP signals for training a transmit sector combination that is tobe used for MIMO transmission by the responder device, the transmissioncircuit transmits to the responder device a third MIMO BF feedback frameincluding feedback information for the plurality of third BRP signals,and the control circuit determines, on the basis of the plurality ofthird BRP signals, a transmit sector combination and a receive sectorcombination that are to be used for MIMO transmission by the initiatordevice.
 9. The initiator device according to claim 8, wherein in adigital BF procedure of a hybrid BF operation that is performed afterthe SU-MIMO BF training, the reception circuit receives from theresponder device a plurality of fourth BRP signals with which theresponder device sounds a channel for a responder link, and thetransmission circuit transmits to the responder device a fourth MIMO BFfeedback frame including feedback information for the plurality offourth BRP signals. 10.-18. (canceled)
 19. A communication method for aninitiator device that supports a single user (SU)-multiple inputmultiple output (MIMO) operation, the communication method comprising:generating a MIMO beamforming (BF) setup frame including anon-reciprocal/reciprocal MIMO phase field that indicates which of anon-reciprocal MIMO phase or a reciprocal MIMO phase is applied toSU-MIMO BF training; transmitting the MIMO BF setup frame to a responderdevice and, in response to the non-reciprocal/reciprocal MIMO phasefield indicating that the reciprocal MIMO phase is applied, transmittingto the responder device a plurality of first beam refinement protocol(BRP) signals for training transmit sectors that are to be used for MIMOtransmission by the initiator device; and receiving from the responderdevice a first MIMO BF feedback frame including feedback information forthe plurality of first BRP signals.
 20. The communication methodaccording to claim 19, wherein in response to the initiator device andthe responder device having antenna pattern reciprocity, thenon-reciprocal/reciprocal MIMO phase field included in the MIMO BF setupframe is set to a first value indicating that the reciprocal MIMO phaseis applied to the SU-MIMO BF training.
 21. The communication methodaccording to claim 19, comprising: determining, on the basis of thefeedback information for the plurality of first BRP signals, a transmitsector combination and a receive sector combination for an initiatorlink.
 22. The communication method according to claim 21, comprising: ina digital BF procedure of a hybrid BF operation that is performed afterthe SU-MIMO BF training, receiving from the responder device a pluralityof second BRP signals for training a transmit sector combination that isto be used for MIMO transmission by the responder device; andtransmitting to the responder device a second MIMO BF feedback frameincluding feedback information for the plurality of second BRP signals.23. The communication method according to claim 21, comprising:receiving from the responder device a training (TRN) signal for traininga transmit sector combination that is to be used for MIMO transmissionby the responder device, the TRN signal being added to the first MIMO BFfeedback frame, and transmitting to the responder device a third MIMO BFfeedback frame including feedback information for the TRN signal. 24.The communication method according to claim 21, comprising: in responseto the non-reciprocal/reciprocal MIMO phase field indicating that thereciprocal MIMO phase is applied to the SU-MIMO BF training, receivingfrom the responder device a plurality of third BRP signals for traininga transmit sector combination that is to be used for MIMO transmissionby the responder device; transmitting to the responder device a thirdMIMO BF feedback frame including feedback information for the pluralityof third BRP signals; and determining, on the basis of the plurality ofthird BRP signals, a transmit sector combination and a receive sectorcombination that are to be used for MIMO transmission by the initiatordevice.
 25. The communication method according to claim 24, comprising:in a digital BF procedure of a hybrid BF operation that is performedafter the SU-MIMO BF training, receiving from the responder device aplurality of fourth BRP signals with which the responder device sounds achannel for a responder link; and transmitting to the responder device afourth MIMO BF feedback frame including feedback information for theplurality of fourth BRP signals.